One can equate such use of keywords as like a hunter using a shotgun, he or she might hit everything in front of the gun, but do you want to kill the tree, rabbit, squirrel, and the prey all at the same time?
Better use one precisely defined keyword or term in a few well selected ways. You then write strong content around the keyword and produce a much tighter controlled article, which the search engines like and also a reader might like. They might even click on your advertisements too, or seek out your other articles.
This approach is more like the sniper with a rifle. One shot and one target. Getting the right keyword will bring your reader to you, by the search engine, the reader finds what they want and you have done a perfect job. They might even click on an ad to reward you.
Writing online should be just as much about providing the reader with what they want. OK you want earnings so place advertising on your site but if you do not provide the reader with anything more than meaningless words with no real information or entertainment, Why should you be expecting a reader to stay, read and look at your work, let alone click on your ads which you spent hours researching keywords for.
Remember keep the use of keywords down to a minimum. I have deliberately loaded this post with a particular keyword just to give an example. See if you can be your own search engine on this article, read it as English prose then consider it as text for a search engine looking for keywords.
Anyone care to tell me what the keyword for this article was?
I have also created an Amazon aStore which sells items intended to advise you about optimizzation of your website and posting to bring potential customers to your pages. You will find books (both paper and Kindle) along with DVD's and MP3 downloads. This aStore is linked to my Amazon Affiliate account and I receive a small payment from Amazon if you decide to purchase any item. I do not record any personal information about you, the aStore is connected directly to Amazon.com and all purchases are guaranteed by them under their normal terms and conditions.
Bretsuki's Search Engine Optimization Store